Recommendation? 220V for grinder - 20 or 30 amps

J

Jeremiah West

Joined
Jul 18, 2019
Messages
4
Hello all,

I am wondering if I could get some opinions on this.

I am having an electrician come to put a 220 line to my garage. I am planning to run a 2HP motor/kbac27D VFD combo. due to budget restrictions a subpanel is out of the question for the next little while so it will just be the one line. I would like to eventually get a heat treat oven and possibly a bench top mill down the road.

I believe that for my grinder it seems that 20A should be sufficient but I have also seen 30A recommended in some posts on here. Is their any advantage/disadvantage to having one or the other? Is their anything else I need to consider before getting an electrician to quote for this?
 
Stacy E. Apelt - Bladesmith said:
Any 220 circuit in the shop should be wired for 30 amps. That allows you to use a HT oven, welder, plasma cutter, big motor, etc. on that socket.
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Definitely 30 amps. It will avoid the need to upgrade in the future. You might also consider having more than one receptacle installed for future uses, such as the equipment you described.
 
Your grinder won't pull 10 amps of 220. You may only need 10-20 amps of 220 for your oven, depending on the oven. But running 30 amps won't cost much extra and you'll able to use the grinder while the heat treat oven is on.

I have a 220V AC unit, plasma cutter and grinder on one run.

You're probably looking at running either size 10 or size 8 wire. The cost difference probably won't be $50. The size of the wiring determines the size breaker you can run. The size breaker you run determines how much power you can pull. It's okay to run multiple items on the same circuit at the same time. That breaker isn't for protecting the machines from an overload, it's to protect the wiring from overheating. I like to run extra to cover future growth.
 
You didn't say if the garage is attached or not. Either way I'd run a 4 conductor cable so you have a neutral and can mount a small $20 sub panel to be able to safely run 120v and 220v circuits.


As a electrician if it's detached depending on the distance I'd run a 30amp FOUR wire circuit, sit a small 12 space SUB panel. Then like everyone else said above you can easily put a couple 120v circuits or a couple 220 circuits. If your using direct burial wire if your going with 10/4 for 30 amp to go up in size is unreasonable in cost. Best to jump up to direct burial 100 amp aluminum mobile home feeder cable and of course sit a 100 amp sub panel then. Or run PVC conduit and pull individual wires rated for wet location.

If garage is attached and not doing UG then the difference in price between 10/4 and 8/4 like Nathan said isn't that terrible.
 
It is an attached garage and fairly short run. It’s only a single car garage. So in reality there is only so much I will be able to fit inside - plus I have been making knives with files for a few years and I really want to just get the grinder going ASAP.

Had the an electrician come today to quote. He is saying to run both a 30 and hardwire the grinder to a 20 amp circuit. Something about Canadian electrical code now requiring GFCI or AFCI on 220 lines under 30amps. I’m not keen on the hard wiring idea.

Either way i still need to put fuses for the input to VFD as per the kbac manual. Is their a standard way to do this? I was thinking just to get a small project box with some fuse holders in it and put that inline before the VFD.
 
I have no clue on Canadian electrical code. If it was me I'd have him run a 30 amp FOUR wire circuit to said receptacle. Then after he leaves I'd study basic electric and install a 12 space sub panel.
 
Unless it is a dedicated outlet ( AC unit or high draw device) put two or three outlets on each circuit. You won't be likely running 220 multiple devices a the same time.
 
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